This invention relates generally to a safety device for power tools and more specifically to an electric circuit actuating mechanism which when appropriately mounted on a power tool stand, allows the operator to turn on the tool's drive motor by a conscious depression of a relatively small sized push button switch, but permits the motor to be turned off by depression of a relatively broad surface by a body part and especially by a body part other than the hands of the operator whereby there is no need for the operator to take his eyes or hands off the work and the cutting or abrading tool.
U.S. Pat. Nos. 3,312,799; 4,166,202; and 4,389,550 each describe various forms of switch actuating mechanisms including a broad surface panel member of one type or another pivotally mounted in proximity to the operator's station and this member is mechanically linked to the on/off lever of the toggle switch. Once the motor of the tool is turned on, it may be turned off by bumping the broad surface panel member with one or more parts of the operator's anatomy other than his hands and this operation may be accomplished without having to glance away from the working surface of the tool being used. This, of course, leads to greater safety by preventing accidental or inadvertent movement of the workpiece or hands into a position where they may be injured by the tool.
However, it can be appreciated that due to the hinged mounting of the broad surface in U.S. Pat. Nos. 3,312,799; 4,166,202; and 4,389,550, bumping the broad surface member along the edge adjacent and parallel to the pivot axis as well as adjacent to the pivot axis may not cause the broad surface member to pivot and cause actuation of the switch or result in turning off the motor of the tool. Although other manners of mounting the broad surface members are known such as shown in U.S. Pat. No. 3,233,071, while reducing the possibility that pushing the broad surface member would not cause actuation of the switch, such arrangements did not eliminate the possibility.
Further, the fabrication of prior actuating mechanisms tended to be overly costly to manufacture because of the number of parts involved, making it somewhat difficult to market at a price commensurate with the cost of the tool on which the safety mechanism was adapted to be used.
The present invention according to the preferred teachings provides an electric circuit actuating mechanism of the general type described but is designed to be substantially less complicated in terms of the number of parts and their assembly into a completed article. This has been done while increasing the element of safety for which the earlier devices were designed.
Specifically, the present invention solves problems encountered by prior mechanisms in the field of electric circuit actuation and other needs in the field by providing, in the most preferred form, a front wall movably mounted relative to a housing enabling any point of the front wall to move in an actuating direction and to slide actuating pins of one or more of a multiplicity of de-energizing momentary switches to de-energize an electric circuit, with the electric circuit being energized by an energizing momentary switch which is not actuated by movement of the front wall.
It is accordingly the principal object of the present invention to provide a new and improved safety device for use in conjunction with electrical motor-driven power tools or the like.
Another object of the invention is to provide an electric circuit actuating mechanism for use with electrically powered tools and disposed such that the power may be turned on by the depression of a first switch and turned off through the application of a force against a broad surface.
Yet another object of the invention is to provide an improved safety device for the control of power-driven tools, the safety device including a broad surface movably mounted to a switch box which, in turn, is arranged to be connected at a desired location on a power tool stand whereby the operator's knee, thigh, hip or other part of his anatomy other than his hands may be used to disconnect the power tool from its power supply.